Generally, in the commercial production of maleic anhydride by the catalytic oxidation of hydrocarbons, it is of ultimate importance to use catalysts which give high conversions of hydrocarbons to maleic anhydride.
Maleic anhydride is conventionally prepared by the oxidation of benzene; however, high percentages of converted benzene are lost in the form of carbon oxides. This process creates unnecessary waste in that two carbon atoms are oxidized to useless waste. Unnecessary waste is also created by the process of Russian Pat. No. 385-957 which discloses the preparation of maleic anhydride by the vapor phase oxidation of dicyclopentadiene with air/steam mixture in the presence of activated vanadium-molybdenum catalysts containing phosphorus and promoted with sodium and silver or nickel, or with oxides of cadmium, copper, cobalt and cerium.
The oxidation of 1,3-butadiene to produce maleic anhydride eliminates this waste. This process has been conducted before in the art using various catalysts, for example German Pat. No. 1,900,111 discloses the preparation of maleic anhydride by the catalytic vapor phase oxidation of 4 carbon hydrocarbons in the presence of catalysts of the composition AO.sub.3 --B.sub.2 O.sub.5 --M.sub.2 O.sub.5-- N.sub.x O--R.sub.2 O (in which A is Cr, Mo, W or U; B is V or Nb; M is P As, Sb or Bi; N is Cu, Ag, Fe, Co or Ni; R is Li, Na, K, Cs or Rb; x is 1-2). U.S. Pat. No. 3,904,653 discloses very desirable catalysts containing antimony, molybdenum, vanadium, iron, oxygen, reduced with molybdenum or tungsten and optionally promoted with Bi, P, Co, Cr, W, Cu, Ag, Sn, Ti, Mn, Zn, Ba, K and the like.
The object of the present invention is to provide a process for producing maleic anhydride by the oxidation of 1,3-butadiene with molecular oxygen using novel catalysts with improved yields of maleic anhydride and decreased waste by-products.